Tuesday, March 5, 2013

An hour of exercise won't save you from the perils of sitting

Almost three years ago, I
wrote that sitting can kill you. You may have been hoping that the damage done
by sitting could be offset by doing some strenuous exercise everyday. I’m afraid
not. A new study by Bernard Duvivier and his colleagues from Maastricht
University Medical Centre shows that even an hour of vigorous exercise can’t
compensate for spending the rest of the day in a chair.

The researchers recruited 18 volunteers to participate in
three movement regimens, each lasting four days. In random order, people were
asked to sit for fourteen hours/day (sitting), to sit for thirteen hours per
day but vigorously pedal a stationary bike for one hour each day (exercise), or
to walk for four hours and stand for two hours (minimal intensity). The last
two protocols resulted in the same daily energy expenditure. After completing
each four-day cycle, the subjects took a ten-day break before moving on to the
next regime.

All participants spent the entire four days of each phase hooked
up to monitors that measured both their energy expenditure and whether they
were sitting, lying, standing or active. They were also asked to keep a food
diary and to consume the same number of calories during each movement protocol,
though their choices were not otherwise restricted. Finally, the volunteers
were given stopwatches to remind them to record time spent sitting, standing or
walking at fifteen minute intervals.

You can see the breakdown of the time spent on each activity
below:

Graphical overview of time spent
in different activity categories (sleeping, sitting, standing, cycling and
walking) in the three regimes followed by the participants.

On the morning of day five,
after completing each four-day activity protocol, fasting blood samples were
taken from each participant. Insulin and plasma lipid levels (cholesterol and
triglycerides) did not differ between the sitting and exercise regimes. In
contrast, levels of these molecules were improved after the minimal intensity
protocol. The differences were not great, but consistent and could have implications for people hoping to stave off type II diabetes or cardiovascular disease.

To be
clear, these data do not compare the benefits of vigorous versus low-intensity
exercise. Rather, the experiments highlight the health differences between more
sitting and less sitting. As expected, less sitting is better. More to the
point, one hour of intense exercise per day does not change one’s blood
profile. If you want to avoid the detriments of sitting, you’ll have to spend a
large part of the day on your feet.

Stochastic Scientist? What's up with that?

Why the Stochastic Scientist? As I'm sure you all know, 'stochastic' is another word for 'random', which is what I intend for the focus of this blog. Although my formal training is as a molecular biologist, there are many other fields of science that are also fascinating and beautiful. It's my intention to blog about which ever scientific discovery or invention catches my, and hopefully your, fancy.

I also hope to inspire people to learn more about science. By choosing among a huge variety of scientific endeavors, I'll undoubtably hit upon something that will pique my readers' interest.

I guess I could have called my blog 'The Joy of Science', but that wouldn't have been quite so random.